Oil-free slider bearing material and method of making the material

ABSTRACT

An oil-free bearing material formed on a substrate metal surface, which consists of a porous resin layer integrally sintered with the metal surface, and wherein the said resin consists essentially of one member selected from the group consisting of polycarbonate, polysulfone, and polyphenylene oxide. The resin layer additionally contains up to 30 weight percent of at least one porosity-improving auxiliary ingredient selected from the group consisting of particles of polytetrafluoroethylene, glass and graphite. The porous resin layer additionally includes mineral wax impregnated therein. A method of making the bearing material comprising the steps of wetting desired portions of the metal surface with a solution of the resin dissolved in a solvent thereof, scattering powder particles of the resin onto said portions of the metal surface thus wet, and sintering the metal surface with the resin powder particles to form a porous resin layer integrally sintered directly on the metal surface.

United States Patent Mizuno 1 Mar. 7, 1972 72 Inventor: Koichi Mizuno,Tokyo, Japan [73] Assignee: Taiho Kogyo Co., Ltd., Toyota, Japana partinterest [22] Filed: Sept. 8, 1969 [21] Appl.No.: 856,003

[30] Foreign Application Priority Data Apr. 24, 1969 Japan ..44/31260[52] US. Cl. ..ll7/2l, 117/33, 117/132 C, 117/161 R, 117/168, 252/12,252/12.2 [51] Int. Cl. ..B44d l/094, 844d 1/ 14 [58] FieldofSearch..117/16, 18,21,26, 22, 23, 117/33, 66, 94, 132 C, 161 R, 168; 252/12,12.2; 308/241 [56] References Cited UNITED STATES PATENTS 3,416,94112/1968 Mizuno 117/26 3,438,896 4/1969 Council et al... 252/ 12 3 ,455,864 7/1969 Dodson 260/41 3,464,845 9/ 1969 Osborn et al. ..260/413,471,587 10/1969 Whittemore et al. ..117/132 C 3,508,945 4/ 1970 Haemeret al. ..252/ 12.2 2,689,380 9/ 1954 Tait ..156/306 2,813,041 1l/1957Mitchell et a1 ..117/21 2,979,417 4/1961 Kruger et al. ..117/132 C2,992,137 7/1961 Bunge et al. 17/33 3,059,318 10/1962 Herbert et al..17/21 3,139,357 6/1964 Arnold 252/1 2.2 3,194,702 7/1965 Geller et al. 117/16 3,238,601 3/1966 White ..161/162 3,258,319 6/1966 Cox..... 117/132C 3,380,843 4/1968 Davis ..1 17/18 3,387,985 6/1968 Huber ..117/21Primary Examiner-William D. Martin Assistant ExaminerRaymond M. SpeerAttorney-Young & Thompson [57] ABSTRACT An oil-free bearing materialformed on a substrate metal surface, which consists of a porous resinlayer integrally sintered with the metal surface, and wherein the saidresin consists essentially of one member selected from the groupconsisting of polycarbonate, polysulfone, and polyphenylene oxide. Theresin layer additionally contains up to 30 weight percent of at leastone porosity-improving auxiliary ingredient selected from the groupconsisting of particles of polytetrafluoroethylene, glass and graphite.The porous resin layer additionally includes mineral wax impregnatedtherein. A method of making the bearing material comprising the steps ofwetting desired portions of the metal surface with a solution of theresin dissolved in a solvent thereof, scattering powder particles of theresin onto said portions of the metal surface thus wet, and sinteringthe metal surface with the resin powder particles to form a porous resinlayer integrally sintered directly on the metal surface.

8 Claims, 4 Drawing Figures PATENTEBMAR 7 I972 Paraffin impregnationParaffin impregnation SHEET 1 UF 2 Grain size (mesh) Fig.2

5 I015 20 25 30 -i'- Content mvsmon I ka/c/w M/zu/va ATTORNEYS OIL-FREESLIDER BEARING MATERIAL AND METHOD OF MAKING THE MATERIAL This inventionrelates to an oil-free bearing material and a method of making thematerial, and more particularly to an oil-free slider bearing materialwhich comprises a porous resin layer being integrally sintered with ametal surface and impregnated with mineral wax, and a method therefor.

The method of making the oil-free slider bearing material according tothe present invention comprises wetting a metal surface with a solutionconsisting of a resin and a solvent thereof, said resin being selectedfrom the group consisting of polycarbonate (to be referred to as PC,hereinafter), polysulfone (to be referred to as PS," hereinafter), andpolyphenylene oxide (to be referred to as PPO, hereinafter); scatteringa powder mixture onto the wetted surface, said powder mixture consistingof particles of a resin selected from the group consisting of PC, PS,and PPO, and one or more optional auxiliary ingredients selected fromthe group consisting of graphite, polytetrafluoroethylene (to bereferred to as TFE, hereinafter), glass, molybdenum sulfide (M andtungsten sulfide (W5 sintering the metal surface with resin particles soas to produce a porous resin layer which is integral with the metalsurface; and impregnating the porous resin layer with mineral wax.

The bearing material and the method according to the present inventionare novel in three points; namely, (1) a porous sintered resin layer isformed directly on a substrate metal surface by using one or more ofthree kinds of resins, i.e., PC, PS, and PPO, which are thermoplasticsynthetic resins; (2) a solution of the resin in a solvent thereof isused to attach the resin particles onto the metal surface; and (3) theporous sintered resin layer is impregnated with mineral wax. Bycombining the three novel points, the inventor has succeeded inproviding a novel oil-free slider bearing material and a method ofmaking the material.

There are various kinds of slider bearing materials which have asynthetic resin layer attached onto a metal surface. However, there hasnot been known any bearing material with a sintered resin layer, whichis made by attaching resin particles onto a metal surface by using onlya solvent of the resin, and heating the metal surface with the resinparticles so as to bond the resin particles to the metal surface andweld the individual resin particles with each other by sintering, andalso it has not been known to produce a slider bearing material byimpregnating such sintered resin layer with mineral wax.

The inventor has found that an excellent oil-free slider bearingmaterial can be achieved by impregnating certain thermoplastic resin,e.g., PC, P5, or PPO, with mineral wax, e.g., paraffin, which resin hasoutstanding heat resistance, creep resistance, and shock resistance.Based on such findings, the inventor has worked out a method of makingthe oil-free slider bearing material, which is essentially consisting offorming a porous resin layer on a metal surface, which is integrallysintered with the metal surface, and impregnating the porous resin layerwith mineral wax. The bearing material according to the presentinvention has excellent mechanical strength and rigidity, and obviatesshortcomings of thermoplastic synthetic resins, such as a largecoefficient of thermal expansion and inability of heat conduction. Inother words, the present invention has succeeded in providing a bearingmaterial consisting of a synthetic resin layer, and yet havingsubstantially the same operative properties as those of alloy bearing.Furthermore, the bearing material according to the present invention canbe used for producing an oil-free slider bearing of excellent operativecharacteristics.

Among vast varieties of synthetic resins, thermoplastic resins PC, PS,and PPO are selected in the present invention as the resin material forproducing an excellent oil-freeslider bearing surface on a metalsurface. Here, it should be noted that modified PPO (made by GeneralElectric Co. under Trademark of Noryl) can be used in the bearingmaterial of the present invention, as a kind of PFC. When the aforesaidthermoplastic resin powders are sintered on the metal surface,

this sintered layer has the porosity of 0 to 50 percent by volume, andthe thermoplastic resin particles are firmly or integrally welded to themetal surface. The porosity of the sintered layer widely variesdepending on the grain size of the particles, the heating temperature,and the content of auxiliary ingredients, such as graphite, TF E, M08and WS,.

The auxiliary ingredients in the bearing material of the presentinvention act to improve the bearing properties and wear resistance ofthe material. In order to take advantage of such action of the auxiliaryingredients, in the method of the present invention, the use is made ofless than 30 percent, based on the total weight of the thermoplasticsynthetic resin, of one or more auxiliary ingredients, which areselected from the group consisting of graphite, TFE, glass, M05 and WS,.With such auxiliary ingredients, the porosity of the sintered resinlayer becomes l to 30 percent by volume. By impregnating the sinteredresin layer with mineral wax at a rate of l to 30 weight percent, basedon the total weight of the sintered layer, there is provided the desiredoil-free slider bearing material.

The mineral wax usable in the bearing material according to the presentinvention is, for instance, solid paraffin which is a petroleum wax,microcrystalline wax, ceresin which is a natural petroleum wax, ormontan wax which is known as a fossil wax. The mineral wax, such asthose listed above, is in solid state at room temperature and has amelting point at 50 to l00 C. Accordingly, the process of impregnatingthe sintered resin layer with the mineral wax can be carried out eitherby dipping a metal with the sintered layer into a molten bath of themineral wax at 70 to l20 C., or by scattering particles of the mineralwax onto the sintered resin layer which is kept at 70 to C. Thus, themineral wax is absorbed in interstices between adjacent resin particlesin the sintered resin layer, so that the sintered resin layer isimpregnated with the mineral wax.

In the method according to the present invention, a solution of theaforesaid resin in solvent thereof is applied onto any desired portionof metal surface, all or in part, and then the aforesaid powder mixtureof resin particles with optional auxiliary ingredients is scattered ontothe wetted portion of the metal surface, so that the powder mixture isselectively attached to the aforesaid desired portion only, because onlythe desired portion is wetted, while the remainder of the metal surfaceis kept dry and does not hold particles of the powder mixture. Thus,according to the present invention, the desired sintered layer andaccordingly the desired bearing surface can be made at any part of thesubstrate surface of any configuration, for instance, one or bothsurfaces of a metal plate, peripheral surface of a shaft, one or both ofthe inner and outer surfaces of a pipe, and a part or entire surface ofa planar or curved surface of articles made by machining, e.g., forging,lathing, and the like. The sintered layer should preferably be 0.2 to1.0 mm. thick, and the grain size and the composition of the aforesaidpowder mixture are selected so as to achieve the aforesaid desiredthickness of the sintered layer.

After being impregnated with mineral wax, the sintered resin layer isfinished by machining into a thickness of 0. l 5 to 0.3 mm.

The sintering temperature is preferably 250 to 290 C. for a mixtureconsisting of PC and auxiliary ingredients, 270 to 330 C. for a mixtureconsisting of PS and the auxiliary ingredients, and 300 to 350 C. for amixture consisting of PPO and the auxiliary ingredients. If PPO is used,the sintering operation should preferably be carried out in a hydrogenatmosphere.

Since the sintering temperature is always below 350 C., any metal whichdoes not experience deformation at such sintering temperature can beused as the substrate of the bearing material of the present invention.it is an important feature of the present invention that an oil-freebearing surface can be made with a high dimensional accuracy, becausethe low sintering temperature eliminates dimensional errors caused inthis process. In addition, accurate finishing work can be made on themineral wax impregnated sintered resin layer by machining.

Typical metal usable as the substrate of the bearing material accordingto the present invention is steel, cast iron, copper alloy, aluminumalloy, and the like. If the desired surface of the substrate, made ofany of the aforesaid metals, is thoroughly cleansed and degreased, thethermoplastic synthetic resin particles, e.g., PC, PS, or FPO, canfirmly be welded or sintered to the desired surface by the methodaccording to the present invention. It should be noted that variousadditional surface treatment can be applied to the substrate, inconjunction with the method of the invention. For instance, thesubstrate surface can be roughened by a mechanical, physical, chemical,electrical, or metallurgical process. Furthermore, special coating canbe made on the substrate surface by applying a chemical conversiontreatment or an anodic oxidation treatment thereto.

There are a number of known solvents capable of dissolving PC, PS, andFPO. For instance, PC and PS can easily be dissolved in a halogenatedhydrocarbon. Methylene chloride or ethylene chloride is preferably usedas a solvent of PC and PS. Trichloroethylene or toluene is preferablyused as a solvent of PPO. However, the solvent usable in the method ofthe present invention for dissolving PC, PS, or PPO is not restricted tothe aforesaid preferred agents, but other solvents of the thermoplasticsynthetic resin can also be used. For instance, chlorobenzene, dioxane,xylene, or carbon tetrachloride can be utilized as a solvent. 7

The solution of the synthetic resin in the solvent should have suchfluidity and concentration which are suitable for application onto thesubstrate metal surface. The concentration of the synthetic resin in themost commonly used solution is 20 percent or less. The solution can beapplied onto the substrate metal surface by brushing, dipping orspraying, so as to wet the surface. Immediately after the substratemetal surface is wet, synthetic resin powders are scattered on thesubstrate. After leaving the powders as scattered on the surface forseveral to twentyseconds, excess resin powders are removed by tiltingthe metal surface or by blowing off with compressed air. The syntheticresin powder particles thus scattered on the wet surface quickly beginto dissolve in the solvent, so as to become sticky to the substratemetal surface and between adjacent resin particles with each other, soas to form a layer of a certain thickness. The thickness of thesynthetic resin layer depends on the amount of the solution wetting thesubstrate surface, the grain size of the powder particles, and thequantity of the synthetic resin powder being scattered. In general,large particles produce a thin layer, while small particles produce athick layer due to the high wettability of the solvent. The thickness ofthe synthetic resin layer, in the state as scattered, is 0.5 to 3.0 mm.,and it is reduced to 0.2 to 1.0 mm. upon sintering.

Since the synthetic resin powder particles are attached to the substratemetal surface by means of a solvent so as to form a synthetic resinlayer, the resin powders can be applied to the metal surface of anyconfiguration, regardless of whether the surface is vertically directeddownwards or intricately curved, and the resin particles thus attachedto the metal surface cannot easily be separated therefrom. Furthermore,the resin particles once attached to the metal surface. remain asattached to even after the solvent completely evaporates away from.thesurface, because the resin particles are welded thereto.

The method of applying synthetic resin powders onto the substrate metalsurface, according to the present invention, is not restricted to theaforesaid process of prewetting with a solution containing the resin andthen scattering the resin powders. For instance, the resin powders canbe attached to the substrate metal surface by many other differentprocesses,

depending on the area, the curvature, and the material of the substratesurface to be covered; namely, by prewetting the metal surface with apure solvent of theresin without the resin dissolved therein and thenscattering the resin powders onto the prewet surface; by drying desiredportionsof the substrate surface, wetting the same portions with asolution containing the synthetic resin, and scattering the syntheticresin powders onto the thus wet portions of the surface; or by forming alining on the desired portion of the substrate surface throughprewetting the desired portion with a solution containing the syntheticresin followed by heating the surface at a temperature higher than themelting point of the resin, rewetting the desired portions with asolution containing the resin, and then scattering the resin powdersonto the rewetted surface.

The mean grain size of the powder particles of PC, PS, and FPO usable inthe method of the invention is in the range of 20 to 200 mesh. The grainsize of graphite powder usable in the method according to the presentinvention is l to 50 microns in diameter, while that of TFE particles ispreferably 50 to 320 mesh, if used. ln other words, the grain size ofthe aforesaid synthetic resin and graphite to be used in the methodaccording to the present invention are all commercially available.

Glass powders, MoS powders, and W8 powders of commercially availablesize can be also used in the method of the invention as optionalauxiliary ingredients.

The preferable temperature for producing a porous sintered layer is 250to 290 C. for PC, 270 to 330 C. for PS, and 300 to 350 C. for PPO. Inthe case of PPO, the heating operation for forming the porous layer isdone in a hydrogen atmosphere. lf mineral wax powders are scattered ontothe porous sintered layer at 70 to C. during the cooling of the sinteredlayer from the aforesaid sintering temperature, the mineral wax ismelted and absorbed by the interstices in the porous sintered layer. Itis, of course, possible to impregnate the porous sintered layer, afterbeing cooled to room temperature, with mineral wax by dipping thesubstrate into a molten bath of the mineral wax.

The porosity of the sintered synthetic resin 'layer can suitably becontrolled in the range of 0 to 50 percent. In an oilfree slider bearingmaterial, according to a preferred embodiment of the invention, theporosity of the sintered resin layer is made 1 to 30 percent, and l to30 Wt. percent of mineral wax, basedon the weight of the porous sinteredresin layer is impregnated into the resin layer.

In the following description, the amount of mineral wax used in thebearing material will be expressed in terms ofimpregnation," which isdefined by the following formula.

(weight of mineral wax absorbed by the sintered porous resin layer)(weight of the sintered porous resin PWkPfiWiih? P fgP i i(impregnation) (volume of the sintered resin layer before theimpregnating) !(porosity) The impregnation and the porosity aredetermined by calculation using the weight, thickness, and area of thesintered resin layer, as well as the specific gravity of the mineralwax. The magnitude of the porosity varies depending on the grain size,the kind, and the amount of the resin powder particles being used, aswell as various treating conditions, such as the heating temperature,the kind of solvent used, the concentration of the solvent, the methodof applying the solvent, etc. If the aforesaid factors are all keptconstant, the porosity can also be kept constant,so that theimpregnation of mineral wax can be controlled at the desired value, forinstance, in the range of l to 30 percent.

The amount of graphite powders and TFE powders to be added in thesynthetic resin powders should preferably be less than 30 percent,respectively, and if the content of the graphite powders of TFE powdersexceeds 30 percent, the adhesiveness (firmness) of the welded jointbetween the substrate metal surface and the sintered resin layer isdeteriorated. The content of the glass powders should be less than 15percent,

while that of M08 and WS should preferably be less than percent,respectively.

For a better understanding of the invention, reference is made to theaccompanying drawings, in which:

FIG. 1 is a graph illustrating the relation between the grain size ofresin particles and paraffin impregnation in a sintered layer made ofsuch resin particles;

FIG. 2 is a graph illustrating the relation between the content ofauxiliary ingredients and paraffin impregnation in the sintered resinlayers;

FIG. 3 is a graph showing the relation between frictional temperaturerise of bearing material according to the present invention and paraffinimpregnation in the bearing material; and

FIG. 4 is a graph showing the relation between frictional temperaturerise of bearing material according to the present invention and contentof auxiliary ingredients therein.

In FIG. 1, there is shown the relation between the grain size ofsynthetic resins PC, PS, PPO and NORYL (a PPO derivative) and paraffinimpregnation therein. It is apparent from the figure that the paraffinimpregnation increases with the grain size of the resin particles,because the porosity of a sintered resin layer made by the resinparticles increases as the grain size of the resin particles increases.For instance, when a sintered resin layer is made by using mesh PCparticles, the paraffin impregnation of the sintered resin layer is 10percent, while when the grain size of resin particles for the sinteredsynthetic resin layer is reduced to 80 mesh, the paraffin impregnationis also reduced to five percent. If the grain size of the resinparticles is further reduced to 200 mesh, the paraffin impregnationdiminishes to about one percent. The use of minute resin particles whosegrain size is considerably smaller than 200 mesh will result in a densesintered layer without any interstices therein with a porosity ofnegligible magnitude. The particles of PS and PPO usually have a meltingpoint higher than that of PC particles, and hence, the porosity of PSand FPO is generally larger than that of PC. As a result, the paraffinimpregnation of sintered resin layers made of PS and FPO is generallylarger than that of PC layer. It is apparent from FIG. 1 that thepreferable grain size of the synthetic resin particles for achieving thedesired porosity of the sintered synthetic resin layer should be in therange of 20 to 200 mesh.

FIG. 2 shows the relation between the content of auxiliary ingredients,such as glass powders, graphite powders, TFE powders, M05 powders, andW3 powders in the sintered resin layer made of 80 mesh PC particles, andparaffin impregnation in the sintered resin layer. The graph clearlyshows that the powders of glass, graphite and TFE act to increase theporosity of the sintered resin layer, while the particles of M08 and WSreduce the porosity. More particularly, a sintered resin layerconsisting of PC particles alone has a paraffin impregnation of fivepercent, while the addition of percent of TFE improves the paraffinimpregnation to about 20 percent. The glass is particularly effective inimproving the porosity of the sintered resin layer. In fact, theaddition of 15 percent of glass powders improves the paraffinimpregnation to 25 percent. FIG. 2 also shows that the paraffinimpregnation of the sintered resin layer is reduced, although onlyslightly, by the addition of M08 or WS in the sintered synthetic resinlayer. In short, the use of glass, graphite or TFE, as auxiliaryingredients improves the porosity of the sintered resin layer. Excessiveporosity of the sintered resin layer, however, impairs the mechanicalstrength of the bearing material. Furthermore, the use of such auxiliaryingredients in excess of percent tends to deteriorate the adherence ofthe sintered resin layer with the substrate metal surface. Therefore,the content of the auxiliary ingredients should be less than 30 percent.The use of MoS or W5 tends to reduce the porosity of the sinteredsynthetic resin layer, but acts to improve the sliding characteristicsof the bearing material by reducing the coefficient of friction thereof.The inventor has found that the use of less than 30 percent of MoS or WSis effective in improving the sliding characteristics of the bearingmaterial, without causing any adverse effects thereon.

FIG. 3 shows the relation between the paraffin impregnation and thefrictional temperature rise. The frictional temperature rise wasmeasured by using a wear testing machine, in which test pieces, preparedby providing the bearing material according to the present invention onsteel sheets, were subjected to dry friction under the conditions of 20l(g./cm. loading while sliding at a rate of one m./sec. The temperaturerise of a bearing surface cooperating with each test piece (asdetermined by subtracting room temperature from the measuredtemperature) proved to be reduced as the paraffin impregnationincreased. In other words, as the paraffin impregnation increases, theheat quantity generated by friction is reduced. In the case of testpieces A (with a sintered resin layer consisting of 75 percent PC, 20percent TFE, and five percent WS and B (with a sintered resin layerconsisting of percent PS, 17 percent TFE, and three percent graphite),the temperature rise decreases as the paraffin impregnation in thesintered resin layer increases, until the paraffin impregnation becomes10 percent, and the temperature rise becomes substantially constant forparaffin impregnation larger than 10 percent. In the case of the testpiece C (with a sintered resin layer consisting of percent PPO, fivepercent glass, and five percent graphite), the temperature rise iscomparatively high due to the existence to the glass particles, but theactual values of the temperature rise decrease as the paraffinimpregnation increases.

As can be seen from the curves of the test pieces A, B, and C in FIG. 3,even a very small paraffin impregnation reduces the temperature rise toa great extent. In fact, the test piece A with no paraffin impregnationhas temperature rise of 65 C., while the use of only 2.5 percentparaffin impregnation results in a drastic reduction of the temperaturerise, i.e., from 65 to 30 C. Thus, the paraffin impregnation hasoutstanding effects on the improvement of bearing material. According tothe present invention, there is provided bearing material which contains1 to 30 percent of paraffin impregnated therein. As pointed out in theforegoing, the use of paraffin in excess of 30 percent requires aporosity of the sintered resin layer, which is larger than 30 percent,and such large porosity impairs the mechanical strength of the bearingmaterial. Accordingly, the paraffin impregnation in the bearing materialof the invention is limited to 30 percent or less.

FIG. 4 illustrates the relation of the content of graphite, TFE, M05 andW8 in paraffin wax, which is to be impregnated into a sintered resinlayer made of 40 mesh PC particles (with a porosity of about eightpercent, as seen from FIG. I), and the frictional temperature rise ofthe bearing material with such paraffin impregnation. It is apparentfrom the figure that the addition of graphite, TFE, M05 and W8 in theparaffin, which is to be impregnated in the sintered resin layer, alsoimproves the sliding characteristics of the bearing material. Among suchauxiliary additives to paraffin, TFE powders are particularly effective.In fact, the frictional temperature rise of the bearing material whichis impregnated with paraffin alone is 38 C., as determined by theaforesaid method, while the addition of 10 percent TFE reduces thetemperature rise to 20 C. Similar improvement can be achieved by theaddition of graphite, M08 or W8 powders.

Thus, the inventor has found that a bearing material of the invention,which consists of a sturdy sintered resin layer made on a substratemetal surface with PC, PS, or FPO powders alone and paraffinimpregnation containing the aforesaid additive and being impregnated inthe sintered resin layer, has both the improved wear resistance and theimproved sliding characteristics? In other words, it is one of theimportant features of the invention to use paraffin, which contains oneor more minute particles (with a mean diameter preferably smaller than10 microns) of graphite, TFE, M05 and WS for the purpose of impregnatingthe sintered resin layer on the substrate metal surface to make thedesired slider bearing material. The content of graphite, TFE, M08 or WSminute powders in paraffin is limited to 15 percent, in the presentinvention. When more than 15 percent of such minute powder particles isadded, the minute particles are filtered in the interstices of thesintered resin layer, and the particles thus added are not distributedhomogeneously.

1n the test pieces, which were used in the measurements related to FIGS.1 to 4, paraffin was used as mineral wax to impregnate the sinteredresin layer. The mineral wax of the present invention is, however, notrestricted to such paraffin alone, but any suitable mineral wax can beused. For instance, microcrystalline wax, ceresin wax, montan wax, andother waxes can similarly be used for achieving the same functions andeffects. Especially, the ceresin wax produces better results thanparaffin.

The mineral wax to be used in the bearing material according to thepresent invention should have a melting point at 50 to 100 C. Two ormore mineral waxes can be used in the bearing material of the inventionat any desired ratio to achieve the same effects as those provided by asingle kind of mineral wax. For instance, a mixture consisting of 50percent paraffin and 50 percent ceresin wax can be used in an embodimentof the present invention.

Therefore, in a preferred embodiment of the present invention, poroussintered resin layer is formed by using 20 to 200 mesh synthetic resinpowders consisting of PC, PS, or PPO, and less than 30 percent, based onthe weight of the resin layer, of auxiliary ingredient powdersconsisting one or more of graphite, TFE, glass, M08 and W8 and theporous sintered resin layer is impregnated with 1 to 30 percent, basedon the weight of the resin layer, of mineral wax, which mineral wax maycontain less than percent, based on the weight of the resin layer, ofone or more of minute particles of graphite, TFE, M05 and WS,. Operativecharacteristics of the oil-free slider bearing material according to thepresent invention, may be controlled in a wide range, by adjusting theconcentration of the aforesaid different ingredients with the abovelimitations, as well as various other factors, such as the kind andconcentration of the solvent for dissolving the synthetic resin powders,the sintering temperature of the resin powders, the heating temperatureof the wax, etc.

As described in the foregoing, according to the present invention, thereis provided a method for making an oil-freev slider bearing material ona substrate metal surface, independent of the material, size andconfiguration of the substrate, which comprises applying a layer ofresin powder consisting of PC, PS, or PPO and optional auxiliaryingredients of graphite, TFE and the like, sintering the layer of resinpowder so as to form a sintered layer, and impregnating the sinteredresin layer with mineral wax, such as paraffin. It is possible to applymachine work on the sintered resin layer formed on steel sheet,according to the present invention, such as by rolling into a certainthickness, by cutting into a desired size, or by bending or by pressinginto a desired configuration. By impregnating the thus machined sinteredresin layer with a suitable mineral wax, there is provided rolledbushes, thrust washers, and other special slider bearing surface ofintricate shape. Similarly, by forming a sintered resin layer on adesired portion of the peripheral surface of a shaft, such as asteelshaft, a cast iron shaft, or a stainless steel shaft, and by suitablymachining the sintered resin layer and impregnating the sintered resinlayer with proper mineral wax, there is provided a rotary shaft whichneed not any conventional complicated shaft bearing.

Furthermore, the bearing surface according to the present inventionshows excellent performance characteristics without necessitating anyoiling. It is one of the important features of the present inventionthat a substrate metal surface is lined with a wax-impregnated resinlayer, so as to eliminate. the aforesaid shortcomings of conventionalbearing materials, such as excessively large thermal expansion and lowheat conductivity. In other words, the present invention providesoilfree slider bearing material which is usable as an outstandingindustrial machine element, and thus contributes greatly to theindustry.

The invention will now be described in further detail, referring toexamples.

Example 1 Oil-free slider bearing material was lined on one side of acontinuous steel belt. A 1.0 mm.-thick and 130 mm.-wide continuous steelstrip was degreased and pickled. A liquid mixture consisting of 15percent of PC and percent of a solvent,

which was comprised of methylene chloride and dioxane, was

applied onto one side of the steel strip by spraying. The strip thus wetby the liquid mixture was passed through slit while scattering, justprior to entering the slit, a powder mixture by a hopper disposed abovethe steel strip. The powders were consisting of 86 percent of 150 meshPC, 10 percent of mesh TFE, two percent of 100 mesh graphite, and twopercent of 100 mesh glass.

Immediately after the passing through the slit, excess powders on thesteel strip were removed by directing compressed air thereto from an aircompressor. A sintered resin layer was formed by heating the strip at270 C. while passing through a furnace, and after cooling to 70-80 C. inthe open air, paraffin powders were scattered onto the sintered resinlayer.

Thus, a 0.4 mm.-thick sintered layer of a bearing material was achieved.The sintered layer thus formed was continu- Example 2 A liningconsisting of bearing material of the invention,

using PPO powder, was formed on a part of the stainless slider of a foodprocessing machine.

The slider weighed 1.205 grams before treating for applying the lining.That portion of the slider, which was to be lined, was degreased andpolished by an abrasive paper. A trichloroethylene solution containing10 percent of PPO dissolved therein was brushed onto the thus cleansedportion of the slider, and a thin film was formed on the slider byheating it at 320 C. in a hydrogen atmosphere. The sametrichloroethylene solution was again brushed'onto the thin film to wetthere, and mesh PPO powders were scattered on the wet surface of theslider. The slider was heated at 330 C. in a hydrogen atmosphere to forma 0.35 mm.-thick sin tered resin layer. The slider with the sinteredresin layer weighed 1,218 grams. In other words, the sintered layerweighed 13 grams.

The sintered resin layer was then impregnated with ceresinpowders'containing five percent of graphite, by scattering the powderson the sintered resin layer while heating the layer at 80 to 100 C. Theamount of the ceresin powders with five percent of graphite, which wasabsorbed by or impregnated in the sintered resin layer, was 2.1 grams.In other words, the content ,of mineral wax, inclusive of graphite, inthe'bearing material lined on the stainless slider was about 16 percent(100X2. l/l 3). The thickness of the bearing material layer was reducedto 0.2 mm. by machining.

.The slider thus lined with the bearing material of the invention provedto have outstanding performance characteristics.

Example 3 desired portion of the dried surface to wet there. Immediatelyafter the wetting, a powder mixture was scattered on the wet portion ofthe shaft surface, and the excess powder on the wet surface was removedby tilting the shaft. The powder mixture was consisting of 91 percent of30 mesh PS, five percent of 200 mesh TFE, and four percent of 200 meshglass.

The shaft covered by the resin powder layer was heated at 290 C., untilthe resin was properly sintered. After being cooled, the shaft with thesintered resin layer was weighed and found to be 831.5 grams. In otherwords, the sintered resin layer weighed 5.5 grams.

The shaft was then dipped into a molten bath of microcrystalline wax at90 C. for impregnating the sintered resin layer with themicrocrystalline wax. By suitably weighing, it was found that 1.1 gramsof the wax was absorbed by the sintered resin layer. in other words, thecontent of the wax in the bearing material was about 20 percent (lOOXl.l [5.5). The lined portion of the shaft was then machined into 26.00 mm.dia., or 0.20 mm. in the thickness of the bearing material.

The shaft thus lined with the bearing material of the invention provedto have excellent performance characteristics.

Example 4 The inner surface of an aluminum bronze alloy bush was linedwith the bearing material of the invention.

The surface, which was to be lined, was cleansed and wet by dipping intoa solution ofmethylene chloride containing 15 percent of PC. A powdermixture was scattered on the surface thus wet, which consisted of 85percent of PC and 15 percent of graphite. By heating at 280 C., asintered resin layer was formed on the inner surface of the bush. Afterbeing cooled, the bush was then dipped in a molten bath of paraffincontaining 10 percent of TFE, so as to be impregnated with the paraffin.The bearing material thus formed on the inner surface of the bushcontained percent of the paraffin with TFE.

The inner surface of the bush with the aforesaid lining was machined andfinished into the desired dimension. The lining on the inner surface ofthe bush proved to be an excellent oilfree slider bearing member.

Example 5 A sliding guide surface was fonned by depositing the bearingmaterial of the invention on one side of a 9.80 mm.-thick 100 mm.-wideand 400 mm.-long aluminum alloy sheet, which weighed 1,162 grams. Thebearing material thus deposited, of course, comprised a sintered resinlayer impregnated with mineral wax, or paraffin in this Example.

After being degreased and pickled, the aluminum alloy sheet was wet bydipping into a liquid mixture, which consisted of 15 percent of PC andthe remainder of methylene chloride and ethylene chloride. Immediatelyafter the wetting, a powder mixture was scattered on the wet surface,and the excess was removed by tilting the sheet. The powder mixtureconsisted of 75 percent of PC, 23 percent of TFE, and two percent of W5A sintered resin layer was formed by heating the sheet with the resinpowder in a furnace at 290 C. for about 40 minutes.

The sheet after the heating weighed 1,182 grams, or the sintered resinlayer weighed grams. The sheet was then dipped into a molten bath ofparaffin at 70C., to impregnate the sintered resin layer with theparaffin. Immediately after the sheet was taken out of the moltenparaffin bath, excess paraffin was removed by wiping with a cloth. Afterbeing cooled, the sheet with the paraffin impregnated resin layer wasweighed, and it was found that the amount of paraffin absorbed in thesintered resin layer was 4.0 grams. Thus, the content of paraffin in thefinal bearing material layer was about 20 percent (l00 4. 0/20.0). Thethickness of the sintered resin layer was about 0.6 mm. before theimpregnation, but the finished sheet with the bearing material of theinvention was machined to a thickness of 10.0 mm. In other words, thethickness of the bearing material layer of the invention on the finishedsheet was 0.2 mm.

Although the present invention has been described while referring topreferred embodiments, it should be understood that numerous changes andmodifications are possible without departing from the scope of theinvention, as will be claimed hereinafter.

What is claimed is:

1. In an oil-free bearing, comprising a substrate metal surface and abearing resin layer formed on the metal surface and consistingessentially of at least one member selected from the group consisting ofpolycarbonate, polysulfone, and polyphenylene oxide; the improvement inwhich the bearing resin layer is a porous resin layer directly sinteredon the metal surface.

2. An oil-free bearing according to claim 1, additionally including amineral wax impregnated in the porous resin layer.

3. An oil-free bearing according to claim 2, in which said mineral waxis at least one member selected from the group consisting of solidparaffin, microcrystalline wax, ceresin, and montan wax.

4. An oil-free bearing according to claim 1, in which said resin layercontains up to 30 weight percent of at least one porosity-improvingauxiliary ingredient selected from the group consisting of particles ofpolytetrafluoroethylene, glass and graphite.

5. In a method of making an oil-free bearing having a substrate metalsurface and a bearing resin layer formed on the metal surface andconsisting essentially of at least one member selected from the groupconsisting of polycarbonate, polysulfone, and polyphenylene oxide; theimprovement comprising applying the resin layer to the metal surface bywetting desired portions of the metal surface with a solution of theresin dissolved in a solvent thereof, scattering powder particles of theresin onto saidportions of the metal surface thus wet, so as to causesaid resin powder particles to adhere to said metal sur face uniformly,and sintering the metal surface with the resin powder particles to forma porous resin layer integrally sintered directly on the metal surface.

6. A method of making an oil-free bearing according to claim 5,including in addition, the step of impregnating a the resin powderparticles before the step of scattering, which auxiliary ingredient isat least one member selected from the group consisting ofpolytetrafluoroethylene, glass and graphite.

2. An oil-free bearing according to claim 1, additionally including amineral wax impregnated in the porous resin layer.
 3. An oil-freebearing according to claim 2, in which said mineral wax is at least onemember selected from the group consisting of solid paraffin,microcrystalline wax, ceresin, and montan wax.
 4. An oil-free bearingaccording to claim 1, in which said resin layer contains up to 30 weightpercent of at least one porosity-improving auxiliary ingredient selectedfrom the group consisting of particles of polytetrafluoroethylene, glassand graphite.
 5. In a method of making an oil-free bearing having asubstrate metal surface and a bearing resin layer formed on the metalsurface and consisting essentially of at least one member selected fromthe group consisting of polycarbonate, polysulfone, and polyphenyleneoxide; the improvement comprising applying the resin layer to the metalsurface by wetting desired portions of the metal surface with a solutionof the resin dissolved in a solvent thereof, scattering powder particlesof the resin onto said portions of the metal surface thus wet, so as tocause said resin powder particles to adhere to said metal surfaceuniformly, and sintering the metal surface with the resin powderparticles to form a porous resin layer integrally sintered directly onthe metal surface.
 6. A method of making an oil-free bearing accordingto claim 5, including in addition, the step of impregnating a mineralwax in the porous resin layer.
 7. A method of making an oil-free bearingaccording to claim 6, in which the mineral wax is at least one memberselected from the group consisting of solid paraffin, microcrystallinewax, ceresin, and montan wax.
 8. A method of making an oil-free bearingaccording to claim 5, including in addition, the step of adding up tO 30weight percent of a porosity-improving auxiliary ingredient to the resinpowder particles before the step of scattering, which auxiliaryingredient is at least one member selected from the group consisting ofpolytetrafluoroethylene, glass and graphite.